Non-volatile memory device, operating method thereof, and storage device having the same

ABSTRACT

A storage device including, a plurality of non-volatile memories configured to include a memory cell region including at least one first metal pad; and a peripheral circuit region including at least one second metal pad and vertically connected to the memory cell region by the at least one first metal pad and the at least one second metal pad, and a controller connected to the plurality of non-volatile memories through a plurality of channels and configured to control the plurality of non-volatile memories, wherein the controller selects one of a first read operation mode and a second read operation mode and transfers a read command corresponding to the selected read operation mode to the plurality of non-volatile memories, wherein one sensing operation is performed to identify one program state among program sates in the first read operation mode, and wherein at least two sensing operations are performed to identify the one program state among the program states in the second read operation mode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/029,265 filed on Sep. 23, 2020, which is a continuation-in-partapplication of U.S. patent application Ser. No. 16/744,763 filed on Jan.16, 2020, now U.S. Pat. No. 10,916,314 issued on Feb. 9, 2021, which isa continuation of U.S. patent application Ser. No. 16/141,294 filed onSep. 25, 2018, now U.S. Pat. No. 10,559,362, issued on Feb. 11, 2020,which claims priority under 35 U.S.C. § 119 to Korean Patent ApplicationNo. 10-2018-0016347, filed on Feb. 9, 2018 in the Korean IntellectualProperty Office, the disclosures of which are incorporated by referenceherein in their entireties.

1. TECHNICAL FIELD

The present inventive concept relates to a non-volatile memory device,an operating method thereof, and a storage device having the same.

2. DESCRIPTION OF RELATED ART

A semiconductor memory device may be classified as a volatilesemiconductor memory device or a non-volatile semiconductor memorydevice. A volatile semiconductor memory device may have stored contentsdisappear, when a power supply is cut off. On the other hand, thenon-volatile semiconductor memory device may preserve its contents, whena power supply is cut off. Therefore, the non-volatile semiconductormemory device may be used to store contents to be preserved, in theabsence of power.

A flash memory device may be an example of the non-volatile memorydevice. The flash memory device may be widely used as a voice and imagedata storage medium in a variety of information devices, such ascomputers, mobile phones, smartphones, digital cameras, camcorders,voice recorders, MP3 players, personal digital assistants (PDAs),handheld computers, game machines, fax machines, scanners, printers, orthe like. Currently, high capacity, high-speed input/output, and lowpower consumption non-volatile memory devices are being researched foruse in mobile devices such as smart phones.

SUMMARY

According to an exemplary embodiment of the present inventive concept, anon-volatile memory device includes: a memory cell region including atleast one first metal pad; a peripheral circuit region including atleast one second metal pad and vertically connected to the memory cellregion by the at least one first metal pad and the at least one secondmetal pad, a memory cell array disposed to the memory cell region andconfigured to include a plurality of memory blocks, each of the memoryblocks includes a plurality of memory cells being programmed, erased, orread by voltages supplied via bit lines and word lines; an addressdecoder disposed to the peripheral circuit region and configured toselect a word line of the word lines in response to an address; a pagebuffer disposed to the peripheral circuit region and configured to sensedata from memory cells connected to the selected word line in a readoperation; an input/output buffer disposed to the peripheral circuitregion and configured to transfer the sensed data to an external devicein the read operation; and a control logic disposed to the peripheralcircuit region and configured to control the page buffer, the addressbuffer, and the input/output buffer in the read operation, wherein thecontrol logic performs a first read operation having at least twosensing operations on a program state among program states; determines alevel of read voltage to identify at least one program state lower thanthe program state according to results of the at least two sensingoperations, and performs a second read operation using the determinedlevel.

According to an exemplary embodiment of the present inventive concept, aoperating method of a non-volatile memory device includes: thenon-volatile memory device configured to include a memory cell regionincluding at least one first metal pad; and a peripheral circuit regionincluding at least one second metal pad and vertically connected to thememory cell region by the at least one first metal pad and the at leastone second metal pad, the operating method comprising, performing afirst read operation having at least two sensing operations on a programstate among program states; determining a level of read voltage toidentify at least one program state lower than the program stateaccording to results of the at least two sensing operations; andperforming a second read operation using the determined level.

According to an exemplary embodiment of the present inventive concept, astorage device comprising, a plurality of non-volatile memoriesconfigured to include a memory cell region including at least one firstmetal pad; and a peripheral circuit region including at least one secondmetal pad and vertically connected to the memory cell region by the atleast one first metal pad and the at least one second metal pad; and acontroller connected to the plurality of non-volatile memories through aplurality of channels and configured to control the plurality ofnon-volatile memories, wherein the controller selects one of a firstread operation mode and a second read operation mode and transfers aread command corresponding to the selected read operation mode to theplurality of non-volatile memories, wherein one sensing operation isperformed to identify one program state among program sates in the firstread operation mode; and wherein at least two sensing operations areperformed to identify the one program state among the program states inthe second read operation mode.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present inventive concept will bemore clearly understood by describing in detail exemplary embodimentsthereof with reference to the accompanying drawings, in which:

FIG. 1 is a block diagram of a non-volatile memory device according toan exemplary embodiment of the present inventive concept;

FIG. 2 is a block diagram illustrating a cell array and a page buffer ofFIG. 1, according to an exemplary embodiment of the present inventiveconcept;

FIG. 3 is a block diagram of a page buffer of FIGS. 1 and 2, accordingto an exemplary embodiment of the present inventive concept;

FIG. 4 is a diagram illustrating a normal read method of a memory cell,according to an exemplary embodiment of the present inventive concept;

FIG. 5 is a flowchart of a read method of a non-volatile memory deviceaccording to an exemplary embodiment of the present inventive concept;

FIG. 6 is a flowchart of an On-Chip Valley Search (OCVS) read operationaccording to an exemplary embodiment of the present inventive concept;

FIG. 7 is a timing diagram illustrating an OCVS read operation by readvoltages having different levels according to an exemplary embodiment ofthe present inventive concept;

FIG. 8A is a timing diagram illustrating an OCVS read operation by alatching signal provided at different times according to an exemplaryembodiment of the present inventive concept;

FIG. 8B is a waveform diagram illustrating a change in the level of asensing node under conditions of control signals of FIG. 8A, accordingto an exemplary embodiment of the present inventive concept;

FIG. 9 is a timing diagram illustrating an example of applying an OCVSread operation according to the exemplary embodiments of FIGS. 8A and 8Bto an uppermost bit page of a triple level cell TLC;

FIGS. 10A, 10B, and 10C are diagrams illustrating a method of selectingdata using latch results of three sensing nodes according to three readsignals, respectively, according to an exemplary embodiment of thepresent inventive concept;

FIGS. 11A, 11B, 11C, and 11D are diagrams illustrating a method ofselecting data using latch results of two sensing nodes according to tworead signals, respectively, according to an exemplary embodiment of thepresent inventive concept;

FIG. 12 is a flowchart of a read method of a non-volatile memory deviceaccording to an exemplary embodiment of the present inventive concept;

FIG. 13 is a diagram illustrating a read operation of FIG. 12, accordingto an exemplary embodiment of the present inventive concept;

FIG. 14 is a timing diagram illustrating the application of a readoperation of FIG. 13 to an center bit page of a triple level cell TLC,according to an exemplary embodiment of the present inventive concept;

FIG. 15 is a timing diagram illustrating the application of a readoperation of FIG. 13 to a center bit page of a triple level cell TLC,according to an exemplary embodiment of the present inventive concept;

FIG. 16 is a diagram illustrating a read operation of FIG. 12, accordingto an exemplary embodiment of the present inventive concept;

FIG. 17 is a diagram illustrating a read operation of FIG. 12, accordingto an exemplary embodiment of the present inventive concept;

FIG. 18 is a diagram illustrating a read operation of FIG. 12, accordingto an exemplary embodiment of the present inventive concept;

FIG. 19 is a diagram illustrating of a non-volatile memory deviceimplemented with C2C structure according to an exemplary embodiment ofthe present inventive concept; and

FIG. 20 is a block diagram illustrating a Solid State Drive (SSD) systemto which a non-volatile memory system according to an exemplaryembodiment of the present inventive concept is applied.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, exemplary embodiments of the present inventive concept willbe described with reference to the accompanying drawings. Like numeralsmay refer to like elements in the drawings.

In the following, a NAND type flash memory device may be used as anexample of a non-volatile memory device for explaining features andfunctions of the present inventive concept. It is to be understood,however, that exemplary embodiments of the present inventive concept maybe applied to phase-change random access memory (PRAM), magnetoresistiveRAM (MRAM), resistive RAM (ReRAM), ferroelectric RAM (FRAM), NOR flashmemory, or the like.

FIG. 1 is a block diagram of a non-volatile memory device according toan exemplary embodiment of the present inventive concept. Referring toFIG. 1, a non-volatile memory device 100 may include a cell array 110,an address decoder 120, a page buffer 130, an input/output buffer 140, acontrol logic 150, a voltage generator 160, and a cell counter 170.

The cell array 110 may be connected to the address decoder 120 via wordlines WLs or selection lines SSL and GSL. The selection lines mayinclude string selection lines SSL and ground selection lines GSL. Thecell array 110 may be connected to the page buffer 130 via bit linesBLs. The cell array 110 may include a plurality of memory blocks BLK0 toBLKi, and each of the memory blocks BLK0 to BLKi may include a pluralityof NAND cell strings. Each channel of cell strings may be formed in avertical or horizontal direction. The cell array 110 may include aplurality of memory cells forming cell strings. The plurality of memorycells may be programmed, erased, and read by a voltage supplied via thebit line BLs or the word line WLs. A program operation may be performedon a page basis, and an erase operation may be performed on a memoryblock (BLK0 to BLKi) basis. Each of the memory blocks BLK0 to BLKi mayinclude a three-dimensional memory array.

The address decoder 120 may select any one of the memory blocks BLK0 toBLKi of the cell array 110 in response to an address ADD. The addressdecoder 120 may select any one of the word lines WLs of the selectedmemory block in response to the address ADD. The address decoder 120 maytransfer a voltage of a word line VWL corresponding to the operationmode to the word line of the selected memory block. The voltage of theword line VWL may also be referred to as a wordline voltage. In aprogram operation, the address decoder 120 may transfer a programvoltage Vpgm and a verification voltage Vfy to a selected word line(e.g., Selected WL), and a pass voltage Vpass to an unselected word line(e.g., Unselected WL). In a read operation, the address decoder 120 maytransfer a selected read voltage Vrd to a selected word line (e.g.,Selected WL), and an unselected read voltage Vread to an unselected wordline (e.g., Unselected WL).

The page buffer 130 may be operated as a writing driver or a senseamplifier. In a program operation, the page buffer 130 may transfer abit line voltage corresponding to data to be programmed to bit lines BLsof the cell array 110. In a read operation, the page buffer 130 maysense data stored in the selected memory cell through one of the bitlines BLs, for example. Each of a plurality of page buffers PB1 to PBnincluded in the page buffer 130 may be connected to one or two bit linesBLs.

Each of the plurality of page buffers PB1 to PBn may perform a latchingoperation for sensing and storing data of selected memory cells toperform an On-Chip Valley Search (OCVS) read operation. Each of theplurality of page buffers PB1 to PBn may perform a plurality of sensingoperations to identify a state of any one of the selected memory cellsunder control of the control logic 150.

For example, assuming that a physical page is composed of a plurality ofbit pages, one piece of page data of a plurality of page dataconstituting one bit page may be read out from an identification of onestate of the memory cells. Each of the plurality of page buffers PB1 toPBn may store sensed data through a plurality of sensing operations, andmay select any one of a plurality of stored data. Each of the pluralityof page buffers PB1 to PBn may perform sensing a plurality of times toidentify a state of any one of the memory cells, for example, toidentify one piece of page data of the plurality of page data. Each ofthe plurality of page buffers PB1 to PBn may select or output optimaldata from a plurality of sensed data under control of the control logic150.

The input/output buffer 140 may transfer externally provided data Datato the page buffer 130. The input/output buffer 140 may transfer anexternally provided command CMD to the control logic 150, and transferan externally provided address ADD to the control logic 150 or theaddress decoder 120. In addition, the input/output buffer 140 may outputdata latched by the page buffer 130 to the outside. For example, theinput/output buffer 140 may output data to a device other than thenon-volatile memory device 100.

The control logic 150 may control the page buffer 130 and the addressdecoder 120 in response to the command CMD externally provided throughthe input/output buffer 140. The control logic 150 may control the pagebuffer 130 and the address decoder 120 to perform program, reading, anderase operations on memory cells selected according to the command CMD.

In particular, the control logic 150 may control the page buffer 130 andthe voltage generator 160 in an OCVS read operation according to anexemplary embodiment of the present inventive concept. The control logic150 may control the page buffer 130 to perform a plurality of sensingoperations to identify a specific state of selected memory cells. Thecontrol logic 150 may control the plurality of page buffers PB1 to PBn,to store data corresponding to each of a plurality of sensingoperations, in a plurality of latches provided in each of the pluralityof page buffers PB1 to PBn. The control logic 150 may perform a processfor selecting optimal data from data sensed a plurality of times. Foroptimal data selection, the control logic 150 may refer to a countresult nC provided from the cell counter 170. For example, the controllogic 150 may control the page buffer 130 to select and output a readingresult closest to a distribution valley among a plurality of senseddata. The control logic 150 may include an OCVS circuit 155 to performthis operation.

The voltage generator 160 may generate various types of word linevoltages VWLs to be supplied to each of the word lines WLs under controlof the control logic 150. The voltage generator 160 may also generate avoltage to be supplied to a bulk, for example, a well region. The wordline voltages VWLs to be supplied to each of the word lines WLs mayinclude a program voltage Vpgm, a pass voltage Vpass, selected andunselected read voltages Vrd and Vread, or the like.

The cell counter 170 may count memory cells corresponding to a specificthreshold voltage range from data sensed in the page buffer 130. Forexample, the cell counter 170 may process data sensed and stored in eachof the plurality of page buffers PB1 to PBn to count the number ofmemory cells having a threshold voltage of a certain threshold voltagerange.

The non-volatile memory device 100 according to an exemplary embodimentof the present inventive concept may perform a plurality of sensingoperations on selected memory cells. The non-volatile memory device 100may select optimal data from a plurality of sensing data, and output theselected data to the outside. According to an exemplary embodiment ofthe present inventive concept, a non-volatile memory device may selectdata sensed by an optimal read voltage, such that data having highreliability may be provided.

FIG. 2 is a block diagram illustrating the cell array 110 and the pagebuffer 130 of FIG. 1, according to an exemplary embodiment of thepresent inventive concept. Referring to FIG. 2, page buffers PB1 to PBnmay be respectively connected to bit lines BL1 to BLn. The bit lines BL1to BLn may be connected to cell strings CS1 to CSn.

The cell strings CS1 to CSn included in the cell array 110 may beconnected to the bit lines BL1 to BLn through string selectiontransistors SST, respectively. Gates of each of the string selectiontransistors SST may be connected to a string selection line SSL. Thecell strings CS1 to CSn may be connected to a common source line CSL viaa ground selection transistor GST, respectively. The gates of each ofthe ground selection transistors GST may be connected to groundselection lines GSL. Each of the cell strings CS1 to CSn may include aplurality of memory cells MC1 to MCn connected to a plurality of wordlines WL1 to WLn, for example.

The page buffer PB1 may be connected to the cell string CS1 through thebit line BL1. The page buffer PB1 may set up or precharge the bit lineBL1 during a program operation. In a read operation, the page buffer PB1may precharge the bit line BL1, and may sense whether a selected memorycell is on or off. The page buffer PB1 may include transistors forsupplying a power supply voltage to the bit lines BL1 to BLn. The pagebuffer PB1 may be provided with a control signal S_CNTL from the controllogic 150 for controlling transistors. The control signal S_CNTL mayinclude a plurality of control signals BLSHF and BLSLT. The bit linesBL1 to BLn may be precharged and developed by the control signals BLSHFand BLSLT.

FIG. 3 is a block diagram of a page buffer of FIGS. 1 and 2, accordingto an exemplary embodiment of the present inventive concept. Referringto FIG. 3, a page buffer PB1 connected to a bit line BL1 may beconnected to memory cells of a cell string CS1 (see FIG. 2). The pagebuffer PB1 may include a sensing node SO connected to the bit line BL1.The page buffer PB1 may include a plurality of latches LT_1, LT_2, LT_3,. . . , LT_C, respectively, connected to the sensing node SO. Aplurality of transistors NM4, NM5, NM6, . . . , NM7 are disposed betweenthe latches LT_1, LT_2, LT_3, . . . , LT_C and respectively receivesignals MON_1, MON_2, MON_3, . . . , MON_C, for example.

In a read operation, the bit line BL1 may be precharged by the controllogic 150. For example, when a load signal LOAD and a control signalBLSHF are activated, the bit line BL1 may be precharged to a specificlevel VBL. At this time, a high-voltage transistor HNM1 may be keptturned on by a bit line selection signal BLSLT. A transistor NM2 may beconnected between a terminal of the high-voltage transistor HNM1 andground and receive signal SHLD, for example.

Subsequently, when the load signal LOAD is inactivated, charges chargedin the sensing node SO may flow to the bit line BL1 through a transistorNM1 turned on by the control signal BLSHF. For example, a developmentoperation in which a change in electric potential of the sensing node SOoccurs may be performed. When a selected memory cell is an on cell,charges charged in the sensing node SO may be discharged to a commonsource line CSL through the bit line BL1 and the channel of the stringCS1. In this case, since an electric current flowing from the sensingnode SO to the bit line BL1 is relatively high, a speed of a voltagedrop of the sensing node SO may be relatively fast. On the other hand,when a selected memory cell is an off cell, charges charged in thesensing node SO may not be discharged to the common source line CSLthrough the bit line BL1. Therefore, since an electric current flowingfrom the sensing node SO to the bit line BL1 is relatively low, thespeed of the voltage drop of the sensing node SO may be relatively slow.

The plurality of latches LT_1, LT_2, LT_3, . . . , LT_C may be providedwith latch control signals LTCH_1, LTCH_2, LTCH_3, . . . , Dump forsensing and storing the developed state of the sensing node SO. Theplurality of latches LT_1, LT_2, LT_3 . . . . , LT_C may sense theselected memory cells a plurality of times according to the latchcontrol signals LTCH_1, LTCH_2, LTCH_3, . . . , Dump, and may store aplurality of sensed data. In one example, the latch control signalsLTCH_1, LTCH_2, LTCH_3, . . . , Dump may be sequentially provided.

According to an exemplary embodiment of the present inventive concept,the plurality of latches LT_1, LT_2, LT_3, . . . , LT_C may perform alatching operation for sensing a plurality of times and storing aplurality of sensed data, to read one state of selected memory cells inan OCVS read operation, for example, to identify one piece of page dataamong a plurality of page data. In the OCVS read operation, according toa plurality of mad signals, e.g., a read signal set, a read voltagehaving a plurality of different levels may be provided to word lines ofselected memory cells, or a plurality of latching signals may beprovided to a plurality of latches at different times from each other.On/off states of the memory cells selected according to the plurality ofread signals may be sequentially stored in the plurality of latchesLT_1, LT_2, LT_3, . . . , LT_C. In this case, the read signals may be acontrol signal for determining a level of read voltage or a latchingtime of the latching operation. For example, the read signal maydetermine a level of the mad voltage or a latching time of the latchingoperation. As will be described later, a change in the latching time mayhave effects corresponding to changing the level of the read voltage.Hereinafter, for convenience, the level of the read signal and the levelof the read voltage may be interchangeably described.

The cell counter 170 may use data stored in the plurality of latchesLT_1, LT_2, LT_3, . . . , LT_C to count the number of memory cells whosethreshold voltage is present between read voltages having differentlevels from each other. For example, data sensed by a first read voltagemay be stored in each of first latches LT_1 of the page buffers PB1 toPBn, while data sensed by a second read voltage may be stored in each ofsecond latches LT_2 of the page buffers PB1 to PBn. In this case, thefirst latches LT_1 of each of the page buffers PB1 to PBn may bereferred to as a first latch set, and the second latches LT_2 of each ofthe page buffers PB1 to PBn may be referred to as a second latch set.When an exclusive OR (XOR) operation is performed between bits stored inthe first latches LT_1 of the page buffers PB1 to PBn and bits stored inthe second latches LT_2 of the page buffers PB1 to PBn, the number ofmemory cells having a threshold voltage between the first read voltageand the second read voltage may be calculated. Further, according to anexemplary embodiment of the present inventive concept, the calculationand comparison of the number of memory cells having a threshold voltagebetween the first read voltage and the second read voltage may beperformed using a current comparator in the form of a differentialamplifier according to a value of bits stored in respective latches.

Any one of the latches, for example, the latch LT_1, may be controlledsuch that only states of the sensing nodes SO are sequentially latched,and each of the plurality of latches LT_2, LT_3, . . . , LT_C may becontrolled such that the sensed data is copied from the latch LT_1. Inaddition, any one of the latches, for example, the latch LT_C, may beused for outputting data of a selected one of the latches.

FIG. 4 is a diagram illustrating a normal read method of a memory cell,according to an exemplary embodiment of the present inventive concept.Referring to FIG. 4, a page-by-page read method of a triple level cellTLC capable of storing 3 bits of data per cell may be illustrated as anexample. Then, an operation of the present inventive concept will bedescribed on the assumption that the memory cell is a triple level cellTLC. However, a method to be described later may involve a quadruplelevel cell QLC capable of storing 4 bits of data per cell, and may beapplied to a multiple level cell capable of storing 4 bits of data ormore.

The triple level cell TLC may include a physical page including aplurality of logic pages. For example, the plurality of logic pages mayinclude a least significant bit (LSB) page, a center bit (CSB) page, anda most significant bit (MSB) page.

To read the least significant bit (LSB) page, a read voltage RD1 may beprovided to word lines of selected memory cells. A memory cell having athreshold voltage lower than the read voltage RD1 may be stored as alogic ‘1,’ and a memory cell having a threshold voltage higher than theread voltage RD1 may be stored as a logic ‘0.’ Then, a read voltage RD5may be provided to the word lines of the selected memory cells. A memorycell having a threshold voltage lower than the read voltage RD5 may bemaintained at a previously stored logic ‘0.’ A memory cell having athreshold voltage higher than the read voltage RD5 may be toggled from apreviously stored logic ‘0’ to a logic ‘1.’ And, after this process iscompleted, a reading result of the least significant bit (LSB) page maybe output.

To read the center bit (CSB) page, a read voltage RD2 may be firstprovided to word lines of selected memory cells. A memory cell having athreshold voltage lower than the read voltage RD2 may be stored as alogic ‘1,’ and a memory cell having a threshold voltage higher than theread voltage RD2 may be stored as a logic ‘0.’ Then, a read voltage RD4may be provided to the word lines of the selected memory cells. A memorycell having a threshold voltage lower than the read voltage RD4 may bemaintained at a previously stored logic ‘0,’ and a memory cell having athreshold voltage higher than the read voltage RD4 may be toggled from apreviously stored logic ‘0‘ to a logic’1.’ Finally, a read voltage RD6may be provided to the word lines of the selected memory cells. A memorycell having a threshold voltage lower than the read voltage RD6 may bemaintained at a previously sensed logic value, and a memory cell havinga threshold voltage higher than the read voltage RD6 may be toggled to alogic ‘0.’ After this process is completed, the reading result of thecenter bit (CSB) page may be output.

To read the most significant bit (MSB) page, a read voltage (RD3) may beprovided to word lines of selected memory cells. A memory cell having athreshold voltage lower than the read voltage RD3 may be stored as alogic ‘1,’ and a sensing result of a memory cell having a thresholdvoltage higher than the read voltage RD3 may be stored as a logic ‘0.’Then, a read voltage RD7 may be provided to the word lines of theselected memory cells. A memory cell having the threshold voltage lowerthan the read voltage RD7 may be maintained at a previously stored logic‘0,’ and a memory cell having the threshold voltage higher than the readvoltage RD7 may be toggled from a previously stored logic ‘0’ to logic‘1.’ After this process is completed, a reading result of the mostsignificant bit (MSB) page may be output.

In this normal read operation, a “read fail” may occur due todeterioration of the memory cell. The non-volatile memory device 100according to an exemplary embodiment of the present inventive conceptmay perform an OCVS read operation to provide high reliability accordingto an external request or an internal judgment, and may provide theresult thereof to the outside.

Although, in the above description, two or three read voltages areprovided to read page data of one bit page of the triple level cell TLC,four or more read voltages may be provided, according to an exemplaryembodiment of the present inventive concept.

FIG. 5 is a flowchart of a read method of a non-volatile memory deviceaccording to an exemplary embodiment of the present inventive concept.Referring to FIG. 5, the non-volatile memory device 100 may perform anormal read operation mode or an OCVS read operation mode according to apredetermined read operation mode.

In operation S110, the non-volatile memory device 100 may confirm a setvalue related to a requested read operation. In other words, thenon-volatile memory device 100 may confirm a predetermined value. In oneexample, the control logic 150 may check whether a page requested to beread is a most significant bit (MSB) page, a center bit (CSB) page, or aleast significant bit (LSB) page. In addition, the control logic 150 maycheck an order of applying a read signal to read a selected page. Inaddition, the control logic 150 may check whether a current readoperation mode is a normal read operation mode or an OCVS read operationmode. In the normal read operation mode, a read signal may be providedonce to identify one state for a memory cell, for example, to identifyone piece of page data of a plurality of page data. On the other hand,in the OCVS read operation mode, read signals having different levelsfrom each other may be provided a plurality of times, and a comparisonoperation for sensing data may be performed to identify one state.

In operation S120, it may be determined whether a read operation mode isan OCVS read operation mode. When a read operation mode is not the OCVSread operation mode, in operation S130, the control logic 150 maycontrol the voltage generator 160 and the page buffer 130 to perform anormal read operation in which a read signal is provided once.Accordingly, a read voltage corresponding to a read signal may beprovided to word lines of selected memory cells, and whether theselected memory cells are turned on/off in the page buffer 130 may besensed. Then, in operation S140, the sensed data may be stored in alatch of the page buffer 130. When the predetermined read operation modeis the OCVS read operation mode, in operation S150, the control logic150 may control the voltage generator 160 and the page buffer 130 toperform the OCVS read operation, which provides the read signal aplurality of times. In the OCVS read operation mode, according to aplurality of read signals, for example, a read signal set, a readvoltage having a plurality of different levels may be provided to wordlines of selected memory cells, or a plurality of latching signals maybe provided at different times from each other. In operation S160, thecontrol logic 150 may determine whether the read operation has beencompleted. When the read operation for the memory cells of the selectedpage is determined to be completed, in operation S170, a reading resultcalculated by the normal operation mode or the OCVS read operation modemay be output to the outside. When an additional read operation on theselected memory cells is required, the process may be returned tooperation S120.

FIG. 6 is a flowchart of an OCVS read operation according to anexemplary embodiment of the present inventive concept. Referring to FIG.6, the OCVS read operation shown in operation S150 of FIG. 5 isillustrated.

In operation S151, read signals may be set. The read signals may includeinformation about a reading count, and may include information about alevel of the read signals that determines an interval between the readsignals. The reading count may represent a specific state of theselected memory cells, for example, the number of searches for one pieceof page data among a plurality of page data. In one example, the readingcount may represent the number of times the read signal is provided toidentify an erase state E0 and a program state P1 of a least significantbit (LSB) page, when the selected memory cells are triple level cellsTLC. In another example, the reading count may represent the number oftimes the read voltage of different levels from each other are to beapplied in the threshold voltage interval between the erase state E0 andthe program state P1. Alternatively, the reading count may also refer tothe number of data latches performed at different development points ofthe sensing node, although the same read voltage is provided to theselected memory cells. In this case, the reading count may be set atleast two times. In addition, an interval between read signals may referto a voltage interval between read voltages at different levels fromeach other, or a time interval between data latching operationsperformed at different development times.

In operation S152, according to the read signals, the data of theselected memory cells may be sensed. For example, the data of theselected memory cells may be sensed according to the number of times theread voltages are supplied, and the voltage interval between the readvoltages. Alternatively, the data of the selected memory cells may besensed according to the number of data latches performed at differentdevelopment times and the time interval between data latchingoperations.

In operation S153, the sensed data may be stored in a latch. In thiscase, data obtained by different read signals may be sensed, and storedthrough different latches from each other.

In operation S154, it may be determined whether a current reading countis a predetermined final reading count. In other words, it may bedetermined whether the count of the current read level is equal to afinal read count. A final reading count may correspond to a value set inoperation S151. When a reading count of the currently performed readoperation is not the final reading count, the process may proceed tooperation S155. On the other hand, when a reading count of the currentlyperformed read operation corresponds to the final reading count, theprocess may proceed to operation S156.

In operation S155, the reading count may be counted up, and operationsS152 and S153 may be performed to sense and store data obtained by thecounted up read signal. In operation S156, data obtained by thedifferent read signals may be compared to output any one of readingresults, and selected reading result.

FIG. 7 is a timing diagram illustrating an OCVS read operation by readvoltages having different levels according to an exemplary embodiment ofthe present inventive concept. Referring to FIG. 7, a read voltageprovided to a word line may be varied for an OCVS read operation. Toillustrate this, a case in which an OCVS read operation is applied to amost significant bit (MSB) page of a triple level cell TLC will bedescribed as an example.

For the OCVS read operation of the most significant bit (MSB) page, aread voltage RD3_1 may first be applied to word lines of selected memorycells (e.g., WL (SEL)). A first latching signal LTCH_1 may be activatedby each of the page buffers PB1 to PBn, at the time in which a prechargePRCH for a bit line BL and a sensing SO node, or a development thereofare completed. At this time, data corresponding to the read voltageRD3_1 may be stored in a first latch set.

Then, a read voltage RD3_2 may be applied to the word lines of theselected memory cells (e.g., WL (SEL)). The read voltage RD3_2 may behigher than the read voltage RD3_1, but correspond to a voltage foridentifying the same one state as the read voltage RD3_1. A secondlatching signal LTCH_2 may be activated by each of the page buffers PB1to PBn, at the time in which a precharge PRCH for a bit line BL and asensing node SO, and a development thereof are completed. At this time,data corresponding to the read voltage RD3_2 may be stored in a secondlatch set of the page buffers PB1 to PBn.

A read voltage RD3_3 may be applied to the word lines of the selectedmemory cells (e.g., WL (SEL)). The read voltage RD3_3 may be higher thanthe read voltage RD3_2, but correspond to a voltage for identifying onestate that is the same as the read voltage RD3_1 and the read voltageRD3_2. A third latching signal LTCH_3 may be activated by each of thepage buffers PB1 to PBn, at the time in which a precharge PRCH for a bitline BL and a sensing node SO, and a development thereof are completed.At this time, data corresponding to the read voltage RD3_3 may be storedin the third latch set. When comparing the results stored in the firstto third latch sets thereafter, any one of the latch sets may beselected.

FIG. 8A is a timing diagram illustrating an OCVS read operation by alatching signal provided at different times according to an exemplaryembodiment of the present inventive concept. Referring to FIGS. 3 and8A, an OCVS read operation performed by sensing a sensing node atdifferent development times and storing a plurality of sensing data willbe described in detail.

A precharging operation may be performed from time T0 to time T1. Bitlines BL1 to BLn and sensing nodes SOs connected to the plurality ofpage buffers PB1 to PBn may be charged for precharging. For example,when the control signals BLSHF and BLSLT, and the load signal LOAD areactivated, the sensing node SO and the bit line BL may be precharged toa specific level, respectively. In the precharging operation betweentime T0 and time T1, the signal SHLD of 0V may be applied to thetransistor NM2 of FIG. 3, the control signal BLSLT may have a voltagelevel of VDD+Vth, the control signal BLSHF may have a voltage level ofVDD, and the load signal LOAD may decrease from the voltage level ofVDD, for example.

At time T1, when the load signal LOAD is deactivated to a high level, ap-channel metal oxide semiconductor (PMOS) transistor PM1 may be cutoff, and a supply of electric current from a power supply voltage VDD tothe sensing node SO may be cut off. As a result, a level of the sensingnode SO may be changed, depending on a magnitude of a current flowing toa bit line BL, or depending on whether a memory cell is on or off. Whena selected memory cell is an on cell, an electric current flowing to abit line BL may be relatively large. Therefore, the level of the sensingnode SO may be relatively quickly lowered. On the other hand, when aselected memory cell is an off cell, the level of the sensing node SOmay be maintained at a substantially constant level.

Memory cells located around a distribution valley are memory cellslocated at boundaries between an on cell and an off cell. Therefore, anidentification of an on cell or an off cell of these memory cells mayvary, depending on a development time. For example, when the developmenttime is slightly reduced, the memory cells located around thedistribution valley may be identified as off cells. On the other hand,when the development time is slightly increased, the memory cellslocated around the distribution valley may be identified as on cells.For example, when the development time is advanced, memory cells havinga threshold voltage similar to a read voltage provided on word lines mayincrease the read voltage to provide an effect of sensing the readvoltage. On the other hand, when the development time is delayed, memorycells having a threshold voltage around the read voltage may lower theread voltage to provide an effect of sensing the read voltage.Therefore, sensing the sensing node SO a plurality of times at differentdevelopment times may have the same effect as precharging and sensingthe bit line BL by varying the word line voltage VWL.

A control signal LTCH_1 may be activated at a time advanced by Δt on thebasis of time T2 (e.g., T2−Δt). For example, the control signal LTCH_1for latching a logic value corresponding to a state of the sensing nodeSO may be provided to a first latch LT_1 of each of the page buffers PB1to PBn in the same read voltage situations. At time T2, a control signalLTCH_2 for latching a state of the sensing node SO may be provided to asecond latch LT_2 of each of the page buffers PB1 to PBn. A controlsignal LTCH_3 for latching a state of the sensing node SO may beprovided to a third latch LT_3 of each of the page buffers PB1 to PBn,at the time delayed by Δt on the basis of time T2 (e.g., T2+Δt).

FIG. 8B is a waveform diagram illustrating a level change of a sensingnode under a control signal situation of FIG. 8A, according to anexemplary embodiment of the present inventive concept. Referring to FIG.8B, a level change of a sensing node SO according to a threshold voltagelevel of a memory cell, and a latch result according to a developmenttime may be shown. Time T0 to time T1 may be referred to as aprecharging period (Precharge), time T1 to time T2 may be referred to asa development period (Develop), and a period after a time T2 may bereferred to as a latch period (Latch). On the other hand, a load signalLOAD may be inactivated in the development period, and a control signalBLSHF may be inactivated in the latch period, as illustrated in FIG. 7.

In the precharging period (Precharge), both the load signal LOAD and thecontrol signal BLSHF may be activated to precharge a bit line BL and asensing node SO. In the precharging period (Precharge), a bit linevoltage VBL may be charged to a first voltage level V1. In theprecharging period (Precharge), the sensing node SO may be charged witha sensing node voltage VSO.

At time T1 at which the development period (Develop) starts, the loadsignal LOAD may be inactivated. In this period, the control signal BLSHFmay remain active. Accordingly, charges charged in the sensing node SOmay be moved to the bit line BL according to a threshold voltage stateof memory cell.

In a case of a memory cell (e.g., a Strong Off Cell) in which athreshold voltage is higher than a read voltage, a level change of thesensing node SO may be relatively small. Change in a sensing node (SO)electric potential of the strong off cell in the development period maybe shown by the dashed line (C0). In a case of a memory cell (e.g.,Strong On Cell) in which a threshold voltage is lower than a readvoltage, a level change of the sensing node SO may be relatively large.Change in the sensing node (SO) electric potential of the strong on cellin the development period may be shown by a solid line (C1). In cases ofstrong off cells or strong on cells, a small change in the developmenttime may be not significantly affected.

A change in electric potential of the sensing node SO sensing memorycells with threshold voltages located around a read voltage may be shownby solid lines C2, C3, and C4, respectively. The solid line C2 may showa development trend of a memory cell having a threshold voltage slightlylower than a read voltage. The solid line C3 may show a developmenttrend of a memory cell having a threshold voltage almost similar to aread voltage. The solid line C4 may show a development trend of a memorycell with a threshold voltage slightly higher than a read voltage.

A first latching signal LTCH_1 for latching the sensing node SO of thememory cells may be provided by advancing a latching time by a referencetime, on the basis of time T2. When the sensing nodes SO are latched bythe first latching signal LTCH_1, in cases of a strong off cell and astrong on cell, the sensing nodes SO may be latched by logic valuescorresponding to off cells and on cells, respectively. The memory cellscorresponding to the solid line C2 having a relatively low thresholdvoltage may be latched by logic values corresponding to the on cells,and the memory cells corresponding to the solid lines C3 and C4 may belatched by the logic values corresponding to the off cells.

When the sensing nodes SO are latched by the second latching signalLTCH_2, a logic ‘0’ and a logic ‘1’ may be latched in a case of a strongoff cell (corresponding to C0) and in a case of a strong on cell(corresponding to C1), respectively, as in the case of the firstlatching signal LTCH_1. The memory cells having the threshold voltagecorresponding to the solid line C2 may be latched by a logic valuecorresponding to an on cell. On the other hand, in the case of thememory cell corresponding to the solid line C3, the sensing node SOelectric potential of a trap level V2 may be latched by the secondlatching signal LTCH_2. For example, the logic ‘0’ and logic ‘1’ may notbe clear. Further, the memory cells corresponding to the solid line C4may be latched by logic values corresponding to off cells.

When the sensing nodes SO are latched by the third latching signalLTCH_3, the logic ‘0’ and the logic ‘0’ may be latched in a case of astrong off cell C0 and in a case of a strong on cell C1, respectively,as in the first latching signal LTCH_1. The memory cells having thethreshold voltages corresponding to the solid lines C2 and C3 may belatched by a logic value ‘1’ corresponding to the on cell, and thememory cell corresponding to the solid line C4 may be latched by a logicvalue ‘0’ corresponding to the off cell.

A method of latching a state of a sensing node SO at differentdevelopment times from each other to identify any one state of memorycells has just been described. Depending on the development time, aneffect similar to providing different levels of read voltages to wordlines may be provided.

FIG. 9 is a timing diagram illustrating an example of applying an OCVSread operation according to the exemplary embodiments of FIGS. 8A and 8Bto an uppermost bit page of a triple level cell TLC. Referring to FIG.9, a read operation by a read voltage RD3 and a read operation by a readvoltage RD7 may be performed to read a most significant bit (MSB) pageof the triple level cell TLC by the OCVS method. Thereafter, readrecovery Read Recovery in which voltages of a page buffer and a wordline are initialized may be performed.

First, a bit line BL and a sensing node SO may be precharged for theOCVS read operation by the read voltage RD3. The read voltage RD3 may beprovided to word lines of selected memory cells. When the precharging iscompleted, a development operation in which a change in electricpotential of the sensing node SO is generated according to states ofmemory cells may be performed on the page buffers PB0 to PBn-1 (see FIG.2). States of the memory cells selected by latching signals LTCH_1,LTCH_2, LTCH_3 provided at different development times may besequentially latched. At this time, the latched data may be stored in aplurality of latches provided in each of the page buffers PB1 to PBn.

Then, a bit line BL and a sensing node SO may be precharged for an OCVSread operation by the read voltage RD7. The read voltage RD7 may beprovided to word lines of selected memory cells. When the precharging iscompleted, a development operation in which a change in electricpotential of the sensing node SO is generated according to states ofmemory cells may be performed on the page buffers PB1 to PBn. States ofthe memory cells selected by the latching signals LTCH_1, LTCH_2, LTCH_3provided at different development times may be latched, and the latcheddata may be stored in a plurality of latches provided in each of thepage buffers PB1 to PBn.

Comparison and selection operations on data latched in the latches ofeach of the page buffers PB1 to PBn may be performed during aprecharging period of a read operation by the read voltage RD7. Forexample, the number of memory cells may be counted by comparing datalatched by the first latching signal LTCH_1 and data latched by thesecond latching signal LTCH_2. The number of memory cells may be countedby comparing data latched by the second latching signal LTCH_2 and datalatched by the third latching signal LTCH_3. The number of the countedcells may be compared to select any one of data sets latched by each ofthe latching signals LTCH_1, LTCH_2, LTCH_3. This process is shown as adata fix (Data fix) in FIG. 9.

When the OCVS read operation by the read voltage RD7 is completed, thedata comparison and selection operations may be performed in a pipelinedmanner together with the reading recovery. In the reading recoveryperiod after the OCVS read operation, the bit lines BL and the sensingnodes SO may be restored to an initial voltage level. At this time, anyone of the data sets latched by each of the latching signals LTCH_1,LTCH_2, LTCH_3 under the read voltage (RD7) condition may be selectedthrough the comparison operation. Most significant bit (MSB) data may bedetermined by processing an OCVS read operation result by the readvoltage RD3 and an OCVS reading result operation by the read voltageRD7.

FIGS. 10A, 10B, and 10C are diagrams illustrating a method of selectingdata using latch results of three sensing nodes SO according to threeread signals, respectively, according to exemplary embodiments of thepresent inventive concept. FIG. 10A shows a data selection method in acase in which threshold voltages of memory cells sensed through an OCVSread operation are located on a left side of a distribution valley. FIG.10B shows a data selection method in a case in which threshold voltagesof memory cells sensed through an OCVS read operation are located on aright side of a distribution valley. FIG. 10C shows a data selectionmethod in a case in which threshold voltages of sensed memory cells arelocated around a distribution valley.

Referring to FIGS. 10A, 10B, and 10C, a level of a threshold voltage ofthe memory cell stored in the latch sets may be modeled according to anOCVS read operation to identify two states S1 and S2 of the memory cell.The threshold voltage positions of the memory cells may be represented,as shown in the distribution diagram, when latched at differentdevelopment times from each other or provided with different levels ofread voltages. For example, a state of a sensing node SO to be latchedby each of a first latching signal LTCH_1, a second latching signalLTCH_2, and a third latching signal LTCH_3 under the same read voltagecondition may be matched to data sensed and stored by each of readvoltages {circle around (1)}{circle around (2)}{circle around (3)}.Latch results corresponding to each of the read voltages {circle around(1)}{circle around (2)}{circle around (3)} corresponding to the readsignal will be referred to as a first latch set (e.g., 1st latch set), asecond latch set (e.g., 2nd latch set), and a third latch set (e.g., 3rdlatch set). For example, each of the first latch set (1^(st) latch set),the second latch set (2^(nd) latch set), and the third latch set (3^(rd)latch set) may represent latches storing data latched by the firstlatching signal LTCH_1, the second latching signal LTCH_2, and the thirdlatching signal LTCH_3, respectively.

Under this assumption, memory cells in which a threshold voltage islocated between the read voltages {circle around (1)} and {circle around(2)} may be counted by comparing the first latch set and the secondlatch set. For example, when data latched in each of the first latch setand the second latch set is processed by an exclusive-OR (XOR)operation, the number nC1 of memory cells in which the threshold voltageis located between the read voltages {circle around (2)} and {circlearound (3)} may be counted. Similarly, the number nC2 of memory cells inwhich the threshold voltage is located between the read voltages {circlearound (2)} and {circle around (3)} may also be counted. This countingoperation may be performed in the cell counter 170 shown in FIG. 1.

When the numbers nC1 and nC2 of memory cells are counted, the controllogic 150 may compare a difference value |nC1−nC2| between the numbernC1 of the first memory cells and the number nC2 of the second memorycells, with a first reference value A. On the other hand, when adifference value |nC1−nC2| is higher than the first reference value A,the counted number nC1 of the first memory cells may be compared withthe counted number nC2 of the second memory cells. Data stored in one ofthe first latch set (1st latch set) and the third latch set (3rd latchset) may be selected, according to the result of comparison between thenumber nC1 of the first memory cells and the number nC2 of the secondmemory cells. On the other hand, when the counted number nC1 of thefirst memory cells and the counted number nC2 of the second memory cellsare higher than a second reference value B, it may be determined as areading failure, and a reading recovery (Reading Recovery) may beperformed. In other words, in the event of a read fail, a read recoveryoperation may be performed. Further, when a difference value (nC1−nC2)is lower than the first reference value A, data stored in the secondlatch set (2nd latch set) may be selected. In this case, one of thecounted number nC1 of the first memory cells and the number nC2 of thesecond memory cells may be output without being compared with the secondreference value B. For example, when a difference value |nC1−nC2| islower than the first reference value A, one of the counted number nC1 ofthe first memory cells and the number nC2 of the second memory cells maybe output without being compared with the second reference value B. Inthis case, the first reference value A may define an error exclusionrange.

Referring to FIG. 10A, when the difference value (nC1-nC2) is higherthan the first reference value A, is lower than the second referencevalue B, and the number nC1 of cells is higher than the number of cellsnC2 (nC1>nC2), the control logic 150 may select a latch setcorresponding to the read voltage {circle around (3)} level. Forexample, the reading result corresponding to the distribution valley maybe determined as the data stored in the third latch set (3rd latch set).

Referring to FIG. 10B, when the difference value (nC1−nC2) is higherthan the first reference value A, is lower than the second referencevalue B, and the counted number nC2 of cells is higher than the numberof cells nC1 (nC1<nC2), the control logic 150 may select a latch setcorresponding to the read voltage {circle around (1)} level. Forexample, the reading result corresponding to the distribution valley maybe determined as the data stored in the first latch set (1^(st) latchset).

Referring to FIG. 10C, when the difference value (nC1−nC2) is lower thanthe first reference value A, for example, when the counted number ofcells nC1 and the counted number of cells nC2 are the same (nC1=nC2) orsimilar to each other, or when the difference therebetween is lower thana reference value, the control logic 150 may select a latch setcorresponding to the read voltage {circle around (2)} level. Forexample, the reading result corresponding to the distribution valley maybe determined as the data stored in the second latch set (2^(nd) latchset).

FIGS. 11A, 11B, 11C, and 11D are diagrams each illustrating methods ofselecting data using latch results of two sensing nodes SO according totwo read signals, respectively, according to an exemplary embodiment ofthe present inventive concept. Since FIGS. 11A to 11D are similar toFIGS. 10A to 10C, overlapping descriptions may be omitted, anddifferences may be mainly described.

When the number nC0 of memory cells is counted, the control logic 150may compare the number nC0 of memory cells to a first reference value Aand a second reference value B. The first reference value A may be lowerthan the second reference value B. When the number nC0 of memory cellsis higher than the second reference value B, it may be determined as areading failure, and reading recovery (Reading Recovery) may beperformed. In other words, in the event of a read fail, a read recoveryoperation may be performed. On the other hand, since the first referencevalue A is lower than the second reference value B, the first referencevalue A may define the error exclusion range.

On the other hand, when the number nC0 of the memory cells is higherthan the first reference value A and lower than the second referencevalue B, the number nC1 of the first memory cells and the number nC2 ofthe second memory cells may be compared. Data stored in one of the firstlatch set (1st latch set) and the third latch set (3rd latch set) may beselected, according to the result of comparison between the number nC1of the first memory cells and the number nC2 of the second memory cells.In addition, when the number nC0 of memory cells is lower than the firstreference value A, data stored in any one of the first latch set (1stlatch set) and the second latch set (2nd latch set) may be selected.

Referring to FIG. 11A, when the number nC0 of memory cells is higherthan the first reference value A and lower than the second referencevalue B (e.g., nC1<nC2), the control logic 150 may select a latch setcorresponding to the read voltage {circle around (2)} level. Forexample, the reading result corresponding to the distribution valley maybe determined as the data stored in the second latch set (2^(nd) latchset).

FIG. 11B shows a method of counting memory cells lower than or higherthan a certain level in each of the above-described states S1 and S2.FIG. 11B shows a method of counting the number of memory cells includedin a specific state to be subjected to an OCVS read operation in amultiple level cell (MLC) or a triple level cell TLC.

Referring to FIG. 11B, the number nC1 of memory cells may be calculatedby subtracting the number (2/8) of memory cells allocated to two statesfrom the reading result (e.g., number of on cells) by the read voltage{circle around (1)} level. In addition, the number nC2 of memory cellsmay be calculated by subtracting the number (4/8) of memory cellsallocated to the four states from the reading result (e.g., number ofoff cells) by the read voltage {circle around (2)} level.

Referring to FIG. 11C, when the number nC0 of memory cells is higherthan the first reference value A, lower than the second reference valueB, and the counted number nC1 of cells is higher than the number nC2 ofcells (nC1>nC2), the control logic 150 may select a latch setcorresponding to the read voltage {circle around (1)} level. Forexample, the reading result corresponding to the distribution valley maybe determined as the data stored in the first latch set (1^(st) latchset).

Referring to FIG. 11D, when the number nC0 of memory cells is lower thanthe first reference value A, for example, when the number nC1 of cellsand the number nC2 of cells are identical to (nC1=nC2) or similar toeach other, the control logic 150 may arbitrarily select and output thefirst latch set (1^(st) latch set) or the second latch set (2^(nd) latchset).

In the above-described embodiment, two or three read signals may beprovided, but according to another exemplary embodiment of the presentinventive concept, more than four read signals may be provided to readone piece of page data.

In addition, when an OCVS read operation for providing a plurality ofread signals to identify one piece of page data of selected memory cellsis applied to identify a plurality of page data, a reading time may beincreased.

This may happen when an OCVS read operation is applied to a quad levelcell QLC or the like that stores more data than a triple level cell TLCor the like, since a lot of time is used to latch a plurality of data.Therefore, a precharging period for comparing and selecting the latchperiod and the latched data is increased.

FIG. 12 is a flowchart of a read method of a non-volatile memory deviceaccording to an exemplary embodiment of the present inventive concept.

In operation S1210, the control logic 150 may provide a high-priorityread signal set for reading high-priority page data of a plurality ofpage data constituting one bit page. The high-priority page data may bepage data in which a high-priority read signal set including a pluralityof high-priority read signals is provided to search an optimaldistribution valley. The high-priority page data may be in plural,depending on an exemplary embodiment of the present inventive concept,to provide a different high-priority read signal set for each of thehigh-priority page data. For example, the high-priority page data(s) maycorrespond to page data for identifying each of the highest programstates and the lowest program states among a plurality of page dataconstituting one bit page. Since a high-priority read signal set isprovided, read operation results corresponding to the high-priority pagedata may be latched into a plurality of sets of latches. In operationS1230, the control logic 150 may compare the results of the plurality ofread operations to select one read signal corresponding to the optimaldistribution valley among the plurality of read signals included in thehigh-priority read signal set. In operation S1250, the control logic 150may determine a low-priority read signal corresponding to the selectedhigh-priority read signal. Subsequently, in operation S1270, the controllogic 150 may perform a read operation of the low-priority page dataaccording to the low-priority read signal.

FIG. 13 is a diagram for explaining a read operation of FIG. 12,according to an exemplary embodiment of the present inventive concept.In this embodiment, a read signal set comprising three read signals maybe provided to read a center bit (CSB) page of the triple level cellTLC.

The control logic 150 may provide at least one high-priority read signalset to selected memory cells of the plurality of memory cells, and mayprovide one of the read signals included in each of the at least onelow-priority read signal set, as a low-priority read signal.

In this embodiment, a first read signal set comprising a plurality ofread voltages RD2_1, RD2_2 and RD2_3 may be a high-priority read signalset, a second read signal set comprising a plurality of read voltagesRD6_1, RD6_2 and RD6_3 may be a low-priority read signal set (e.g., asecond low-priority read signal set), and a third read signal setcomprising a plurality of read voltages RD4_1, RD4_2 and RD4_3 may be alow-priority read signal set (e.g., a third low-priority read signalset). Depending on an exemplary embodiment of the present inventiveconcept, the high-priority/low-priority read signal set may be changed.

When the first read signal set including the plurality of read voltagesRD2_1, RD2_2 and RD2_3 is provided, the read operation results of thepage data for distinguishing the program states P1 and P2 among the pagedata may be latched to a plurality of latch sets. The number of memorycells between the plurality of read voltages RD2_1, RD2_2, RD2_3 of thefirst read signal set may be counted from the results of the readoperation.

The control logic 150 may compare the count values of the memory cellsbetween the current read voltages RD2_1, RD2_2, and RD2_3 to select theread signal corresponding to the optimal distribution valley. In thisembodiment, a read signal corresponding to the read voltage RD2_3 shownby a solid line arrow among the read voltages RD2_1, RD2_2 and RD2_3 maybe selected.

The control logic 150 may determine a low-priority read signalcorresponding to the selected read signal in the high-priority readsignal set. The control logic 150 may determine that the read voltageRD6_3 indicated by the solid line arrow corresponding to the level ofthe read voltage RD2_3 among the read voltages RD6_1, RD6_2, and RD6_3of the second low-priority read signal set, is a low-priority readsignal. Similarly, the control logic 150 may determine that the readvoltage RD4_3 indicated by the solid line arrow corresponding to thelevel of the read voltage RD2_3 among the read voltages RD4_1, RD4_2 andRD4_3 of the third low-priority read signal set, is a low-priority readsignal.

The control logic 150 may perform the read operation of the low-prioritypage data according to the read voltage RD4_3 and the read voltage RD6_3determined by the low-priority read signal. In this case, the readoperation according to the read voltage RD4_3 and the read voltage RD6_3determined by the low-priority read signal may correspond to the normalread operation in which one read signal is provided to identify oneoperation.

When a latch set corresponding to a read operation according to the readvoltage RD2_3, a latch set corresponding to a read operation accordingto the read voltage RD6_3, and a latch set corresponding to a readoperation according to the read voltage RD4_3 are combined, a last readdata of the center bit (CSB) page may be output.

In the above description, a low-priority read signal set is provided inadvance, and one of the plurality of read signals in the low-priorityread signal set is described as a low-priority read signal. However, alow-priority read signal corresponding to the read signal may be alsogenerated, rather than having to provide it in advance.

FIG. 14 is a timing diagram illustrating the application of a readoperation of FIG. 13 to a center bit page of a triple level cell TLC,according to an exemplary embodiment of the present inventive concept.FIG. 15 is a timing diagram illustrating the application of a readoperation of FIG. 13 to a center bit page of a triple level cell TLC,according to an exemplary embodiment of the present inventive concept.

Referring to FIG. 14, an OCVS read operation according to a read voltageRD2, and a normal read operation by a read voltage RD6 and a readvoltage RD4 may be performed to read a center bit (CSB) page of a triplelevel cell TLC. Thereafter, a read recovery operation (Read Recovery) inwhich voltages of a page buffer 130 and word lines WL are initializedmay be performed.

First, bit lines BL of the memory cells selected in a precharging periodPRCH and a sensing node SO may be precharged to perform an OCVS readoperation according to the read voltage RD2. Latching signals LTCH_1,LTCH_2, and LTCH_3 may be sequentially provided at a plurality of timesat which the sensing node SO is developed. In other words, the latchingsignals LTCH_1, LTCH_2, and LTCH_3 may be provided in a Develop period.In this case, the latching signal LTCH_2 may correspond to a defaultvalue, and the latching signals LTCH_1 and LTCH_3 may correspond tosignals in which the latching time of the latching signal LTCH_2 hasbeen partially changed to retrieve the optimal distribution valley. Datamay be stored in different latch sets by each of the latching signalsLTCH_1, LTCH_2, and LTCH_3. At this time, the latched data may be storedin a plurality of latches provided in each of the page buffers PB1 toPBn.

Then, the bit line BL and the sensing node SO may be precharged for thenormal read operation by a read voltage RD6. The word line WL ofselected memory cells may be provided with the read voltage RD6. Whenthe precharging is completed, a development operation may be performedin the page buffers PB1 to PBn in which a change in electric potentialof the sensing node SO is generated according to states of memory cells.

In the precharging period of the read operation by the read voltage RD6,comparison and selection operations may be performed on the data latchedin the latches of the page buffers PB1 to PBn by the read voltage RD2.For example, the number of memory cells may be counted by comparing datalatched by the first latching signal LTCH_1 and data latched by thesecond latching signal LTCH_2. The number of memory cells may be countedby comparing the data latched by the second latching signal LTCH_2 withthe data latched by the third latching signal LTCH_3. The number ofcounted cells may be compared to select any one of the data sets latchedby each of the latching signals LTCH_1, LTCH_2, and LTCH_3. This processmay be shown as a data fix (Data Fix) in the FIG. 14. In this case,under the condition of the read voltage RD2, the data set by thelatching signal LTCH_3 may be finally selected.

A latching signal corresponding to the finally selected latching signalLTCH_3 under the condition of the read voltage RD2 may be provided underthe condition of the read voltage RD6. For example, when the bit line BLand the development of the sensing node SO are performed under the readvoltage RD6 condition, the latching signal LTCH_3 is provided such thatthe data may be latched. On the other hand, as described above, thelevel of the read signal may be varied by changing the level of the readvoltage provided to the word line WL, or by changing the latching pointof the sensing node SO. Referring to FIG. 15, in the data fix (Data Fix)period, a precharging period may be overlapped, and thus, a separateprecharging period may be additionally required to change the level ofthe read voltage. Thus, in this embodiment, the latching time of thelatching circuit may be changed. For example, it may be useful to changethe level of the read signal by changing the latching point, rather thanchanging the level of the read signal by changing the read voltage inthe first low-priority read operation after the high-priority readoperation in which the high-priority read signal set is provided. Inaddition, in a situation where one voltage generating circuit isprovided in the voltage generator 160 (FIG. 1) and different voltagesare not provided to each of the plurality of memory blocks BLK0 to BLKi(FIG. 1), when the levels of the signals are different, the level of theread signal by varying the latching time of the sensing node SO may beappropriately varied.

Then, still referring to FIG. 14, the bit line BL and the sensing nodeSO may be precharged for the normal read operation by the read voltageRD4. The word line WL of selected memory cells may be provided with theread voltage RD4. When the precharging is completed, a developmentoperation may be performed in the page buffers PB1 to PBn in which achange in electric potential of the sensing node SO is generatedaccording to the state of the memory cell. When the developmentoperation is performed, the latching signal LTCH_3 corresponding to thefinally selected latching signal LTCH_3 under the condition of the readvoltage RD2 may be provided under the condition of the read voltage RD4such that the data are latched. The center bit (CSB) data may bedetermined by processing the OCVS read operation result by the readvoltage RD2, the normal read operation result by the read voltage RD6,and the normal read operation result by the read voltage RD4.

In FIG. 14, data may be precharged by the read voltage RD4 and data maybe latched by the latching signal LTCH_3. However, in FIG. 15, data isprecharged by a read voltage RD4_3, and data may be latched by thesignal LTCH_2. In this case, the read voltage RD4_3 may correspond to avoltage obtained by partially changing the voltage level according tothe difference between the default read voltage RD4 and the latchingtime LTCH_1 of the default latching signal LTCH_2. For example, the readvoltage RD4_3 corresponding to the selected latching signal LTCH_1 maybe provided to read the second low-priority page data, instead of thelatching signal LTCH_1 selected in the read voltage RD4.

According to an exemplary embodiment of the present inventive concept,the level of the read signal may be changed by changing the level of theread voltage, rather than by changing the latching time in the secondlow-priority read operation after the high-priority read operation inwhich the high-priority read signal set is provided. This maysignificantly reduce the change in the threshold voltage of the memorycells, thereby achieving a high resolution, and therefore may accuratelydetermine the distribution valley.

FIG. 16 is a diagram illustrating a read operation of FIG. 12, accordingto an exemplary embodiment of the present inventive concept. Since theembodiment of FIG. 16 is similar to the embodiment of FIG. 13,overlapping descriptions may be omitted, and differences may be mainlydescribed.

In general, variations in the threshold voltage distribution of memorycells may be varied, depending on the programmed state. In a case of anerase state E0 and a low-priority program state P1, distribution may berelatively spread to the right. Further, in a case of higher programstates P6 and P7, distribution may be spread to the left. Althoughintermediate program states, e.g., P2, P3, P4, and P5, are somewhatdifferent, the spread or shift of the distribution may appear to benegligible.

According to an exemplary embodiment of the present inventive concept,depending on the relationship between the program state of thehigh-priority page data, for example, the program state in which thehigh-priority read signal set is provided, and the program state of thelow-priority page data, for example, the program state in which thelow-priority read signal set is provided, the level of the low-priorityread signal may be determined. For example, the level of thelow-priority read signal may be determined by comparing the spreaddirection of distribution of the high-priority page data and the spreaddirection of distribution of the low-priority page data.

When the spread direction of distribution of the high-priority page datais opposite to the spread direction of distribution of the low-prioritypage data, the level of the selected high-priority read signal may beshifted in the direction opposite the spread direction of distributionof the high-priority page data. This way, the level of the low-priorityread signal is determined. For example, if it is assumed that ahigh-priority read signal set is provided in a low-priority programstate, the level of the selected high-priority read signal may besequentially shifted in one direction, to determine the level of theread signal in the intermediate program state and the higher programstate. In this case, one direction may be a direction opposite thespread direction of distribution in the lower program state, forexample, the left direction. Likewise, if it is assumed that ahigh-priority read signal set is provided to the higher program state,the level of the selected high-priority read signal may be sequentiallyshifted in one direction to determine the level of the read signal inthe intermediate program state and the low-priority program state. Inthis case, one direction may be a direction opposite the spreaddirection of distribution in the higher program, for example, the rightdirection.

The level of the low-priority read signal may be determined by comparingthe spread of the high-priority page data to the spread of the scatteredlow-priority page data, when the spread direction of distribution of thehigh-priority page data is identical to the spread direction ofdistribution of the low-priority page data. For example, when the spreaddegree of distribution of the high-priority page data is higher than thespread degree of distribution of the low-priority page data, the levelof the selected high-priority read signal may be shifted in thedirection opposite the spread direction of distribution of thehigh-priority page data, to determine the low-priority read signal.Likewise, when the spread degree of distribution of the high-prioritypage data is lower than the spread degree of distribution of thelow-priority page data, the level of the selected high-priority readsignal may be shifted in the spread direction of distribution of thehigh-priority page data to determine the level of the low-priority readsignal.

According to an exemplary embodiment of the present inventive concept,the high-priority read signal set may be provided in a program statehaving the highest spread degree to calculate an optimal low-priorityread signal corresponding to the distribution valley.

In FIG. 16, when a read signal corresponding to the read voltage RD2_3is selected among the first read signal set including the plurality ofread voltages RD2_1, RD2_2 and RD2_3, the level of the selected firstread voltage RD2_3 may be shifted. Then, the read voltage RD6_2 may bedetermined to be a low-priority read voltage in an intermediate programstate, and the read voltage RD4_1 may be determined to be a low-priorityread voltage in an higher program state.

FIG. 17 is a diagram illustrating a read operation of FIG. 12, accordingto an exemplary embodiment of the present inventive concept. Since theembodiment of FIG. 17 is similar to the embodiment of FIG. 13,overlapping descriptions may be omitted, and differences may be mainlydescribed. In this embodiment, a read signal set composed of four readsignals may be provided to read the center bit (CSB) page of the triplelevel cell TLC.

The control logic 150 may provide at least one high-priority read signalset to selected memory cells of the plurality of memory cells, and mayprovide one of the read signals included in each of the at least onelow-priority read signal set as a low-priority read signal.

In this embodiment, a first read signal set including a plurality ofread voltages RD2_1, RD2_2, RD2_3 and RD2_4 may be a first high-priorityread signal set, a second read signal set including a plurality of readvoltages RD6_1, RD6_2, RD6_3 and RD6_4 may be a second high-priorityread signal set, and a third read signal set including a plurality ofread voltages RD4_1, RD4_2, RD4_3, and RD4_4 may be low-priority readsignals. According to an exemplary embodiment of the present inventiveconcept, the high-priority/low-priority read signal set may be changed.

When the first high-priority read signal set including the plurality ofread voltages RD2_1, RD2_2, RD2_3 and RD2_4 is provided, the readoperation results of the page data for distinguishing the program statesP1 and P2 may be latched to a plurality of latch sets. The number ofmemory cells between the plurality of read voltages RD2_1, RD2_2, RD2_3,and RD2_4 of the first high-priority read signal set may be counted fromthe results of the read operation. The control logic 150 may compare thecount values of the memory cells between the read voltages RD2_1, RD2_2,RD2_3, and RD2_4 to select the read signal corresponding to the optimaldistribution valley.

When the second high-priority read signal set including the plurality ofread voltages RD6_1, RD6_2, RD6_3 and RD6_4 is provided, the readoperation results of the page data for distinguishing the program statesP5 and P6 may be latched to a plurality of latch sets. The number ofmemory cells between the plurality of read voltages RD6_1, RD6_2, RD6_3,RD6_4 of the second high-priority read signal set may be counted fromthe results of the read operation.

The control logic 150 may compare the count values of the memory cellsbetween the read voltages RD6_1, RD6_2, RD6_3, and RD6_4 to select theread signal corresponding to the optimal distribution valley.

The control logic 150 may determine a low-priority read signal,depending on a read signal selected from the first high-priority readsignal set and a read signal selected from the second high-priority readsignal set.

Table 1 below is provided to illustrate a method for determining alow-priority read signal, depending on read signals selected from afirst high-priority read signal set and a second high-priority readsignal set.

TABLE 1 High-priority read signal Low-priority Read signal 1st RD(RD2)2nd RD(RD6) 3rd RD(RD4) Case 1 RD2_1 RD6_1 RD4_1 Case 2 RD2_1 RD6_2RD4_1 or RD4_2 Case 3 RD2_1 RDS_3 RD4_2 Case 4 RD2_1 RD6_4 RD4_2 orRD4_3 Case 5 RD2_2 RD6_1 RD4_1 or RD4_2 Case 6 RD2_2 RD6_2 RD4_2 Case 7RD2_2 RD6_3 Case2 or RD4_3 Case 8 RD2_2 RD6_4 RD4_3 Case 9 RD2_3 RD6_1RD4_2 Case 10 RD2_3 RD6_2 RD4_2 or RD4_3 Case 11 RD2_3 RD6_3 RD4_3 Case12 RD2_3 RD6_4 RD4_3 or RD4_4 Case 13 RD2_4 RD6_1 RD4_2 or RD4_3 Case 14RD2_4 RD6_2 RD4_3 Case 15 RD2_4 RD6_3 RD4_3 or RD4_4 Case 16 RD2_4 RD6_4RD4_4

Referring to Table 1, in a case that the same level of read signals areselected from the first read signal set (1^(st) RD) corresponding to thefirst high-priority read signal set and the second read signal set(2^(nd) RD) corresponding to the second high-priority read signal set(e.g., Case 1, Case 6, Case 11, and Case 16), a read signal having thesame level among a plurality of read signals of the third read signalset (3^(rd) RD) may be determined as a low-priority read signal. Forexample, in a case that the read voltage RD2_1 is selected in the firsthigh-priority read signal set and the read voltage RD6_1 is selected inthe second high-priority read signal set (e.g., Case 1), the read signalcorresponding to the read voltage RD4_1 in the third read signal set(3^(rd) RD) may be determined as a low-priority read signal.

Further, in a case that read signals having different levels from eachother are selected from the first read signal set (1^(st) RD)corresponding to the first high-priority read signal set and the secondread signal set (2^(nd) RD) corresponding to the second high-priorityread signal set (e.g., Case 2, Case 5, Case 7, Case 10, Case 12, andCase 15), the number of memory cells according to each of the selectedread signals may be counted, to determine one read signal among theplurality of read signals of the third read signal set (3^(rd) RD) as alow-priority read signal. For example, in a case that the read voltageRD2_1 is selected in the first high-priority read signal set, and theread voltage RD6_2 is selected in the second high-priority read signalset (e.g., Case 2), the number of memory cells in the program state P2according to the read voltage RD2_1 may be compared to the number ofmemory cells in the program state P6 according to the read voltageRD6_2, to determine a read signal having a level corresponding to theread voltage having a small number of memory cells as low-priority readsignals. As another example, when the read voltage RD2_1 is selected inthe first high-priority read signal set, and the read voltage RD6_2 isselected in the second high-priority read signal set (e.g., Case 2), thenumber of memory cells in the program state P1 according to the readvoltage RD2_1 may be compared to the number of memory cells in theprogram state P5 according to the read voltage RD6_2, such that a readsignal having a level corresponding to the read voltage having a smallnumber of memory cells may be determined as a low-priority read signal.

Further, when read signals having different levels from each other areselected from the first read signal set (1^(st) RD) corresponding to thefirst high-priority read signal set and the second read signal set(2^(nd) RD) corresponding to the second high-priority read signal set,and an odd number of read signals are present between the selected readsignals having different levels from each other, the level of the readsignal in the middle of the odd number of read signals among theplurality of read signals of the third read signal set (3^(rd) RD) maybe determined as a low-priority read signal. For example, when one readsignal is present between the selected read signals having differentlevels from each other (e.g., Case 3, Case 8, Case 9, and Case 14), aread signal having a level corresponding to one read signal may bedetermined as a low-priority read signal.

Further, when read signals having different levels from each other areselected from the first read signal set (1^(st) RD) corresponding to thefirst high-priority read signal set and the second read signal set(2^(nd) RD) corresponding to the second high-priority read signal set,and an even number of read signals are present between the selected readsignals having different levels from each other (e.g., Case 4, and Case13), the number of memory cells according to each of the selected readsignals is counted to determine one read signal among the plurality ofread signals of the third read signal set (3^(rd) RD) as a low-priorityread signal. For example, when the read voltage RD2_1 is selected in thefirst high-priority read signal set, and the read voltage RD6_4 isselected in the second high-priority read signal set (e.g., Case 4), thenumber of memory cells in the program state P2 according to the readvoltage RD2_1 and the number of memory cells in the program state P6according to the read voltage RD6_4 may be compared to determine thelevel corresponding to the read voltage having a small number of memorycells as the level of the low-priority read signal.

FIG. 18 is a diagram illustrating a read operation of FIG. 12, accordingto an exemplary embodiment of the present inventive concept. Since theembodiment of FIG. 18 is similar to the embodiment of FIG. 17,overlapping descriptions may be omitted, and differences may be mainlydescribed. In this embodiment, a read signal set comprising four readsignals may be provided to read one bit page of a quad level cell QLC.

The control logic 150 may provide at least one high-priority read signalset to selected memory cells of a plurality of memory cells, and mayprovide one read signal included in each of the at least onelow-priority read signal set as a low-priority read signal.

In this embodiment, a first read signal set including a plurality ofread voltages RD13_1, RD13_2, RD13_3, and RD13_4 may be referred to as afirst high-priority read signal set, a second read signal set includinga plurality of read voltages RD3_1, RD3_2, RD3_3, and RD3_4 may bereferred to as a second high-priority read signal set, a third readsignal set including a plurality of read voltages RD7_1, RD7_2, RD7_3,and RD7_4 may be referred to as a first low-priority read signal set,and a fourth read signal set including the voltages RD9_1, RD9_2, RD9_3and RD9_4 may be referred to as a second low-priority read signal set.According to an exemplary embodiment of the present inventive concept,the high-priority/low-priority read signal set may be changed.

When a first high-priority read signal set including the plurality ofread voltages RD13_1, RD13_2, RD13_3 and RD13_4 is provided, readoperation results of page data for distinguishing program states P2 andP3 among page data may be latched to a plurality of latch sets. Thenumber of memory cells between the plurality of read voltages RD13_1,RD13_2, RD13_3, and RD13_4 of the first read signal set may be countedfrom the results of the read operation. The control logic 150 maycompare the count values of the memory cells between the read voltagesRD13_1, RD13_2, RD13_3, and RD13_4 to select the read signalcorresponding to the optimal distribution valley.

When the second read signal set including a plurality of read voltagesRD3_1, RD3_2, RD3_3 and RD3_4 is provided, read operation results ofpage data for distinguishing program states P12 and P13 among page datamay be latched to a plurality of latch sets. The number of memory cellsbetween the plurality of read voltages RD3_1, RD3_2, RD3_3, and RD3_4 ofthe second read signal set may be counted from the results of the readoperation. The control logic may compare the count values of the memorycells between the read voltages RD3_1, RD3_2, RD3_3, and RD3_4 to selectthe read signal corresponding to the optimal distribution valley.

The control logic 150 may determine a low-priority read signal,depending on a read signal selected from the first high-priority readsignal set and a read signal selected from the second high-priority readsignal set.

Table 2 below is provided to illustrate a method for determining alow-priority read signal, depending on read signals selected from afirst high-priority read signal set and a second high-priority readsignal set.

TABLE 2 High-priority read signal Low-priority Read signal 1st RD(RD13)2nd RD(RD3) 3rd RD(RD7) 4th RD(RD 9) Case 1 RD13_1 RD3_1 RD7_1 RD9_1Case 2 RD13_1 RD3_2 RD7_2 RD9_1 Case 3 RD13_1 RD3_3 RD7_2 RD9_2 Case 4RD13_1 RD3_4 RD7_3 RD9_2 Case 5 RD13_2 RD3_1 RD7_1 RD9_2 Case 6 RD13_2RD3_2 RD7_2 RD9_2 Case 7 RDI3_2 RD3_3 RD7_3 RD9_2 Case 8 RD13_2 RD3_4RD7_3 RD9_3 Case 9 RD13_3 RD3_1 RD7_2 RD9_2 Case 10 RD13_3 RD3_2 RD7_2RD9_3 Case 11 RD13_3 RD3_3 RD7_3 RD9_3 Case 12 RD13_3 RD3_4 RD7_4 RD9_4Case 13 RD13_4 RD3_1 RD7_2 RD9_3 Case 14 RD13_4 RD3_2 RD7_3 RD9_3 Case15 RD13_4 RD3_3 RD7_3 RD9_4 Case 16 RD13_4 RD3_4 RD7_4 RD9_4

Referring to Table 2, in a case that the same level of read signals areselected from the first read signal set (1^(st) RD) corresponding to thefirst high-priority read signal set and the second read signal set(2^(nd) RD) corresponding to the second high-priority read signal set(e.g., Case 1, Case 6, Case 11, and Case 16), a read signal having thesame level among each of a plurality of read signals of the third readsignal set (3^(rd) RD) and the fourth read signal set (4^(th) RD) may bedetermined as a low-priority read signal. For example, in a case thatthe read voltage RD13_1 is selected in the first high-priority readsignal set and the read voltage RD3_1 is selected in the secondhigh-priority read signal set (e.g., Case 1), the read signalcorresponding to the read voltage RD7_1 in the third read signal set(3^(rd) RD) may be determined as a low-priority read signal, and theread signal corresponding to the read voltage RD9_1 in the fourth readsignal set (4^(th) RD) may be determined as a low-priority read signal.

Further, in a case that read signals having different levels from eachother are selected from the first read signal set (1^(st) RD)corresponding to the first high-priority read signal set and the secondread signal set (2^(nd) RD) corresponding to the second high-priorityread signal set, and the selected read signals having different levelsfrom each other are adjacent to each other (e.g., Case 2, Case 5, Case7, Case 10, Case 12, and Case 15), the level of the read signal selectedfrom the first high-priority read signal set may be applied to thelow-priority read signal set disposed adjacent to the firsthigh-priority read signal set, and the level of the read signal selectedfrom the second high-priority read signal set may be applied to thelow-priority read signal set disposed adjacent to the secondhigh-priority read signal set. For example, in a case that the readvoltage RD13_1 is selected in the first high-priority read signal set,and the read voltage RD3_2 is selected in the second high-priority readsignal set (e.g., Case 2), the read signal corresponding to the readvoltage RD7_2 in the third read signal set (3^(rd) RD) may be determinedas a low-priority read signal, and the read signal corresponding to theread voltage RD9_1 in the fourth read signal set (4^(th) RD) may bedetermined as a low-priority read signal.

Further, when read signals having different levels from each other areselected from the first read signal set (1^(st) RD) corresponding to thefirst high-priority read signal set and the second read signal set(2^(nd) RD) corresponding to the second high-priority read signal set,and an odd number of read signals are present between the selected readsignals having different levels from each other, the level of the readsignal in the middle of the odd number of read signals may be determinedas a low-priority read signal. For example, when one read signal ispresent between the selected read signals having different levels fromeach other (e.g., Case 3, Case 8, Case 9, and Case 14), a read signalhaving a level corresponding to one read signal may be determined as alow-priority read signal.

Further, when read signals having different levels from each other areselected from the first read signal set (1^(st) RD) corresponding to thefirst high-priority read signal set and the second read signal set(2^(nd) RD) corresponding to the second high-priority read signal set,and an even number of read signals are present between the selected readsignals having different levels from each other (e.g., Case 4, and Case13), a first level close to a level of a read signal selected from thefirst high-priority read signal set may be applied to the low-priorityread signal set disposed adjacent to the first high-priority read signalset, and a first level close to a level of a read signal selected fromthe second high-priority read signal set may be applied to thelow-priority read signal set disposed adjacent to the secondhigh-priority read signal set.

FIG. 19 is a diagram illustrating of a non-volatile memory deviceimplemented with C2C structure according to an exemplary embodiment ofthe present inventive concept.

Referring to FIG. 19, a memory device 1000 may have a chip-to-chip (C2C)structure. The C2C structure may refer to a structure formed bymanufacturing an upper chip including a cell region CELL on a firstwafer, manufacturing a lower chip including a peripheral circuit regionPERI on a second wafer, different from the first wafer, and thenconnecting the upper chip and the lower chip in a bonding manner. Forexample, the bonding manner may include a method of electricallyconnecting a bonding metal formed on an uppermost metal layer of theupper chip and a bonding metal formed on an uppermost metal layer of thelower chip. For example, when the bonding metals may be formed of copper(Cu), the bonding manner may be a Cu—Cu bonding, and the bonding metalsmay also be formed of aluminum or tungsten.

Each of the peripheral circuit region PERI and the cell region CELL ofthe memory device 1000 may include an external pad bonding area PA, aword line bonding area WLBA, and a bit line bonding area BLBA.

The peripheral circuit region PERI may include a first substrate 1210,an interlayer insulating layer 1215, a plurality of circuit elements1220 a, 1220 b, and 1220 c formed on the first substrate 1210, firstmetal layers 1230 a, 1230 b, and 1230 c respectively connected to theplurality of circuit elements 1220 a, 1220 b, and 1220 c, and secondmetal layers 1240 a, 1240 b, and 1240 c formed on the at least one firstmetal layers 1230 a, 1230 b, and 1230 c. In an example embodiment, theat least one first metal layers 1230 a, 1230 b, and 1230 c may be formedof tungsten having relatively high resistivity, and the at least onesecond metal layers 1240 a, 1240 b, and 1240 c may be formed of copperhaving relatively low resistivity.

In an example embodiment illustrate in FIG. 19, although the at leastone first metal layers 1230 a, 1230 b, and 1230 c and the at least onesecond metal layers 1240 a, 1240 b, and 1240 c are shown and described,they are not limited thereto, and one or more metal layers may befurther formed on the at least one second metal layers 1240 a, 1240 b,and 1240 c. At least a portion of the one or more metal layers formed onthe at least one second metal layers 1240 a, 1240 b, and 1240 c may beformed of aluminum or the like having a lower resistivity than those ofcopper forming the at least one second metal layers 1240 a, 1240 b, and1240 c.

The interlayer insulating layer 1215 may be disposed on the firstsubstrate 1210 and cover the plurality of circuit elements 1220 a, 1220b, and 1220 c, the at least one first metal layers 1230 a, 1230 b, and1230 c, and the at least one second metal layers 1240 a, 1240 b, and1240 c. The interlayer insulating layer 1215 may include an insulatingmaterial such as silicon oxide, silicon nitride, or the like.

Lower bonding metals 1271 b and 1272 b may be formed on the at least onesecond metal layer 1240 b in the word line bonding area WLBA. In theword line bonding area WLBA, the lower bonding metals 1271 b and 1272 bin the peripheral circuit region PERI may be electrically connected toupper bonding metals 1371 b and 1372 b in the cell region CELL in abonding manner, and the lower bonding metals 1271 b and 1272 b and theupper bonding metals 1371 b and 1372 b may be formed of aluminum,copper, tungsten, or the like.

The cell region CELL may include at least one memory block. The cellregion CELL may include a second substrate 1310 and a common source line1320. On the second substrate 1310, a plurality of word lines 1331 to1338 (i.e., 1330) may be stacked in a direction (a Z-axis direction),perpendicular to an upper surface of the second substrate 1310. At leastone string select line and at least one ground select line may bearranged on and below the plurality of word lines 1330, respectively,and the plurality of word lines 1330 may be disposed between the atleast one string select line and the at least one ground select line.

In the bit line bonding area BLBA, a channel structure CH may extend ina direction, perpendicular to the upper surface of the second substrate1310, and pass through the plurality of word lines 1330, the at leastone string select line, and the at least one ground select line. Thechannel structure CH may include a data storage layer, a channel layer,a buried insulating layer, and the like, and the channel layer may beelectrically connected to a first metal layer 1350 c and a second metallayer 1360 c. For example, the at least one first metal layer 1350 c maybe a bit line contact, and the at least one second metal layer 1360 cmay be a bit line. In an example embodiment, the bit line 1360 c mayextend in a first direction (a Y-axis direction), parallel to the uppersurface of the second substrate 1310.

In an example embodiment illustrated in FIG. 19, an area in which thechannel structure CH, the bit line 1360 c, and the like are disposed maybe defined as the bit line bonding area BLBA. In the bit line bondingarea BLBA, the bit line 1360 c may be electrically connected to thecircuit elements 1220 c providing a page buffer 1393 in the peripheralcircuit region PERI. For example, the bit line 1360 c may be connectedto upper bonding metals 1371 c and 1372 c in the cell region CELL, andthe upper bonding metals 1371 c and 1372 c may be connected to lowerbonding metals 1271 c and 1272 c connected to the circuit elements 1220c of the page buffer 1393.

In the word line bonding area WLBA, the plurality of word lines 1330 mayextend in a second direction (an X-axis direction), parallel to theupper surface of the second substrate 1310, and may be connected to aplurality of cell contact plugs 1341 to 1347 (i.e., 1340). The pluralityof word lines 1330 and the plurality of cell contact plugs 1340 may beconnected to each other in pads provided by at least a portion of theplurality of word lines 1330 extending in different lengths in thesecond direction. A first metal layer 1350 b and a second metal layer1360 b may be connected to an upper portion of the plurality of cellcontact plugs 1340 connected to the plurality of word lines 1330,sequentially. The plurality of cell contact plugs 1340 may be connectedto the circuit region PERI by the upper bonding metals 1371 b and 1372 bof the cell region CELL and the lower bonding metals 1271 b and 1272 bof the peripheral circuit region PERI in the word line bonding areaWLBA.

The plurality of cell contact plugs 1340 may be electrically connectedto the circuit elements 1220 b providing a row decoder 1394 in theperipheral circuit region PERI. In an example embodiment, operatingvoltages of the circuit elements 1220 b providing the row decoder 1394may be different than operating voltages of the circuit elements 1220 cproviding the page buffer 1393. For example, operating voltages of thecircuit elements 1220 c providing the page buffer 1393 may be greaterthan operating voltages of the circuit elements 1220 b providing the rowdecoder 1394.

A common source line contact plug 1380 may be disposed in the externalpad bonding area PA. The common source line contact plug 1380 may beformed of a conductive material such as a metal, a metal compound, polysilicon, or the like, and may be electrically connected to the commonsource line 1320. A first metal layer 1350 a and a second metal layer1360 a may be stacked on an upper portion of the common source linecontact plug 1380, sequentially. The second metal layer 1360 a iselectrically connected to an upper metal via 1371 a. The upper metal via1371 a is electrically connected to an upper metal pattern 1372 a. Forexample, an area in which the common source line contact plug 1380, theat least one first metal layer 1350 a, and the at least one second metallayer 1360 a are disposed may be defined as the external pad bondingarea PA.

Input-output pads 1205 and 1305 may be disposed in the external padbonding area PA. Referring to FIG. 19, a lower insulating film 1201covering a lower surface of the first substrate 1210 may be formed belowthe first substrate 1210, and a first input-output pad 1205 may beformed on the lower insulating film 1201. The first input-output pad1205 may be connected to at least one of the plurality of circuitelements 1220 a, 1220 b, and 1220 c disposed in the peripheral circuitregion PERI through a first input-output contact plug 1203, and may beseparated from the first substrate 1210 by the lower insulating film1201. In addition, a side insulating film may be disposed between thefirst input-output contact plug 1203 and the first substrate 1210 toelectrically separate the first input-output contact plug 1203 and thefirst substrate 1210.

Referring to FIG. 19, an upper insulating film 1301 covering the uppersurface of the second substrate 1310 may be formed on the secondsubstrate 1310, and a second input-output pad 1305 may be disposed onthe upper insulating layer 1301. The second input-output pad 1305 may beconnected to at least one of the plurality of circuit elements 1220 a,1220 b, and 1220 c disposed in the peripheral circuit region PERIthrough a second input-output contact plug 1303, a lower metal pattern1272 a and a lower metal via 1271 a.

According to embodiments, the second substrate 1310 and the commonsource line 1320 may not be disposed in an area in which the secondinput-output contact plug 1303 is disposed. Also, the secondinput-output pad 1305 may not overlap the word lines 1330 in the thirddirection (the Z-axis direction). Referring to FIG. 19, the secondinput-output contact plug 1303 may be separated from the secondsubstrate 1310 in a direction, parallel to the upper surface of thesecond substrate 1310, and may pass through the interlayer insulatinglayer 1315 of the cell region CELL to be connected to the secondinput-output pad 1305.

According to embodiments, the first input-output pad 1205 and the secondinput-output pad 1305 may be selectively formed. For example, the memorydevice 1000 may include only the first input-output pad 1205 disposed onthe first substrate 1210 or the second input-output pad 1305 disposed onthe second substrate 1310. Alternatively, the memory device 1000 mayinclude both the first input-output pad 1205 and the second input-outputpad 1305.

A metal pattern in an uppermost metal layer may be provided as a dummypattern or the uppermost metal layer may be absent, in each of theexternal pad bonding area PA and the bit line bonding area BLBA,respectively included in the cell region CELL and the peripheral circuitregion PERI.

In the external pad bonding area PA, the memory device 1000 may includea lower metal pattern 1273 a, corresponding to an upper metal pattern1372 a formed in an uppermost metal layer of the cell region CELL, andhaving the same shape as the upper metal pattern 1372 a of the cellregion CELL, in an uppermost metal layer of the peripheral circuitregion PERI. In the peripheral circuit region PERI, the lower metalpattern 1273 a formed in the uppermost metal layer of the peripheralcircuit region PERI may not be connected to a contact. Similarly, in theexternal pad bonding area PA, an upper metal pattern, corresponding tothe lower metal pattern formed in an uppermost metal layer of theperipheral circuit region PERI, and having the same shape as a lowermetal pattern of the peripheral circuit region PERI, may be formed in anuppermost metal layer of the cell region CELL.

The lower bonding metals 1271 b and 1272 b may be formed on the at leastone second metal layer 1240 b in the word line bonding area WLBA. In theword line bonding area WLBA, the lower bonding metals 1271 b and 1272 bof the peripheral circuit region PERI may be electrically connected tothe upper bonding metals 1371 b and 1372 b of the cell region CELL by aCu—Cu bonding.

Further, the bit line bonding area BLBA, an upper metal pattern 1392,corresponding to a lower metal pattern 1252 formed in the uppermostmetal layer of the peripheral circuit region PERI, and having the sameshape as the lower metal pattern 1252 of the peripheral circuit regionPERI, may be formed in an uppermost metal layer of the cell region CELL.The lower metal pattern 1252 is electrically connected to a lower metalvia 1251. A contact may not be formed on the upper metal pattern 1392formed in the uppermost metal layer of the cell region CELL.

In an example embodiment, corresponding to a metal pattern formed in anuppermost metal layer in one of the cell region CELL and the peripheralcircuit region PERI, a reinforcement metal pattern having the same shapeas the metal pattern may be formed in an uppermost metal layer inanother one of the cell region CELL and the peripheral circuit regionPERI, and a contact may not be formed on the reinforcement metalpattern.

Also, details of the C2C structures are described in U.S. applicationSer. No. 16/816,476, filed on Mar. 12, 2020, the disclosure of which isincorporated by reference into this application in its entirety.

FIG. 20 is a block diagram illustrating a Solid State Drive (SSD) systemto which a non-volatile memory system according to an exemplaryembodiment of the present inventive concept is applied. Referring toFIG. 20, the SSD system 2000 may include a host 2100 and an SSD 2200.The SSD 2200 may exchange a signal SIG with the host 2100 through asignal connector 2001, and may receive a power PWR through a powersupply connector 2002. The SSD 2200 may include an SSD controller 2210,a plurality of non-volatile memories 2221-222 n, an auxiliary powersupply device 2230, and a buffer memory 2240. The non-volatile memories2221-222 n may be flash memories.

The SSD controller 2210 may control the plurality of flash memories2221-222 n in response to the signal SIG received from the host 2100.The SSD controller 2210 may select one of a first read operation mode(or normal read operation mode) and a second read operation mode andtransfer a read command corresponding to the selected read operationmode to the plurality of non-volatile memories 2221-222 n. Where onesensing operation is performed to identify on program state amongprogram sates in the first read operation mode, and wherein at least twosensing operations are performed to identify on the program state amongthe program states in the second read operation mode. Also, the secondread operation mode includes an On-Chip Valley Search (OCVS) readoperation mode. Where in the OCVS read operation mode, a read signalset, a read voltage having a plurality of different levels are providedto word lines of selected memory cells, or a plurality of latchingsignals is provided at different times from each other. And the SSDcontroller 2210 may select the second read operation mode when a readoperation is failed in the first read operation mode. For example, Forexample, when error correction is not possible as a result of the errorcorrection operation in the first read operation, a read retry operationusing OCVS read operation may be performed.

The auxiliary power supply device 2230 may be connected to the host 2100through the power supply connector 2002. The auxiliary power supplydevice 2230 may receive and charge the power PWR from the host 2100. Theauxiliary power supply device 2230 may provide power to the SSD system2000, when power is not smoothly supplied from the host 2100. Forexample, the auxiliary power supply device 2230 may be disposed withinthe SSD 2200 or outside the SSD 2200. For example, the auxiliary powersupply device 2230 may be disposed on the main board, and may provide anauxiliary power to the SSD 2200.

The buffer memory 2240 may be operated as a buffer memory of the SSD2200. For example, the buffer memory 2240 may temporarily store datareceived from the host 2100 or data received from the plurality of flashmemories 2221-222 n, or may temporarily store metadata of the flashmemories 2221 to 222 n (for example, a mapping table). The buffer memory2240 may include other non-volatile memories such as dynamic RAM (DRAM),synchronous DRAM (SDRAM), double data rate (DDR) SDRAM, low power DDR(LPDDR) SDRAM, static (SRAM), or the like, or non-volatile memories suchas FRAM, ReRAM, spin transfer torque (STT)-MRAM, PRAM, or the like.

According to an exemplary embodiment of the present inventive concept, aplurality of sensing procedures may be performed to identify a specificpage data state from one bit page, and one sensing procedure may beperformed to identify states of remaining page data to effectivelyreduce time required to read in a read operation. For example, anon-volatile memory device may be configured to sense a plurality oftimes to identify a specific state of a memory cell, and to select andoutput optimal data among the sensed results.

While the present inventive concept has been described with reference toexemplary embodiments thereof, it will be apparent to those skilled inthe art that modifications and variations could be made thereto withoutdeparting from the scope of the present inventive concept as defined bythe appended claims.

What is claimed is:
 1. An operating method of a non-volatile memorydevice, the method comprising, applying first read voltages to aselected wordline for reading least significant bit (LSB) page data;outputting the LSB page data to an external device; applying second readvoltages to the selected wordline for reading center significant bit(CSB) page data; outputting the CSB page data to the external device;applying third read voltages to the selected wordline for reading a mostsignificant bit (MSB) page data; outputting the MSB page data to theexternal device; receiving a command from the external device when atleast one of the LSB page data, the CSB page data, and the MSB page datais uncorrectable; and performing an on-chip valley search read operationin response to the command, wherein the on-chip valley search readoperation includes at least two sensing operations to identify one stateamong program states.
 2. The method of the non-volatile memory deviceaccording to claim 1, wherein the first voltages include a first readvoltage and a fifth read voltage, the second voltages include a secondread voltage, a fourth read voltage and a sixth read voltage, and thethird voltages include a third read voltage and a seventh read voltage.3. The method of the non-volatile memory device according to claim 1,wherein the performing the on-chip valley search read operationcomprises, applying a read signal having different levels to be providedat different times from each other in response to the command to theselected wordline for identifying one state corresponding touncorrectable page data; latching data at the different times; countingthe number of latching data at the different times; performing countingoperations using the counted number of the latching data at thedifferent times; and selecting a page data among the latching data atthe different times according to a result of the counting operation. 4.The method of the non-volatile memory device according to claim 1,wherein the performing the on-chip valley search read operation furthercomprises, confirming a set value related to the command, wherein theconfirming the set value includes selecting a page data to be read isthe LSB page data, the CSB page data, or the MSB page data.
 5. Themethod of the non-volatile memory device according to claim 4, whereinthe confirming the set value further includes checking an order ofapplying read signals to read the selected page data.
 6. The method ofthe non-volatile memory device according to claim 5, wherein the readsignals having different levels from each other are provided to theselected wordline a plurality of times for identifying the one state. 7.The method of the non-volatile memory device according to claim 5,wherein each of the read signals includes a plurality of differentlevels and are provided to the selected wordline at different times fromeach other.
 8. The method of the non-volatile memory device according toclaim 1, wherein the on-chip valley search operation further includescounting the number of memory cells in which a threshold voltage ispresent between read voltages having different levels from each otherafter the at least two sensing operations.
 9. The method of thenon-volatile memory device according to claim 1, wherein the on-chipvalley search operation further includes selecting sensed datacorresponding to one among the at least sensing operation as page dataaccording to a result of the counting.
 10. The method of thenon-volatile memory device according to claim 9, further comprises,outputting the sensed data.
 11. A non-volatile memory device,comprising: a cell array having a plurality of memory blocks, each ofthe memory blocks having a plurality of strings, each of the stringshaving memory cells corresponding a plurality of wordlines and beingconnected between a corresponding bitline among a plurality of bitlinesand a common source line; an address decoder configured to select one ofthe memory blocks in response to an address and to select one of thewordlines in the selected memory block in response to the address; apage buffer circuit having a plurality of page buffers, each of the pagebuffers corresponding to the bitlines configured to perform at least twosensing operations for identifying a state among program states; and acontrol logic configured to control the page buffer circuit and theaddress decoder in response to a command, wherein the command istransferred to an external device when a read operation is failed,wherein the read operation performs one sensing operation foridentifying the state among the program states.
 12. The non-volatilememory device of claim 11, wherein the control logic determines whethera read operation mode is an on-chip valley search read operation modeaccording to the command.
 13. The non-volatile memory device of claim12, wherein the control logic performs the on-chip valley search readoperating using the at least two sensing operation when the readoperations mode is the on-chip valley search read operation mode. 14.The non-volatile memory device of claim 11, wherein the at least twosensing operations are performed corresponding to different read levelsfrom each other.
 15. The non-volatile memory device of claim 11, whereinthe control logic outputs a plurality of latching signals correspondingto at the two sensing operations to the page buffer circuit at differenttimes from each other.
 16. A storage device comprising: a plurality ofnon-volatile memories configured to include a memory cell regionincluding at least one first metal pad; and a peripheral circuit regionincluding at least one second metal pad and vertically connected to thememory cell region by the at least one first metal pad and the at leastone second metal pad; and a controller connected to the plurality ofnon-volatile memories through a plurality of channels and configured tocontrol the plurality of non-volatile memories, wherein the controllerissues a command for performing an on-chip valley search read operationwhen a read failure is generated in a normal read operation, wherein theon-chip valley search read operation includes at least two sensingoperations for identifying one state among program states, and whereinthe normal read operation includes one sensing operation for identifyingthe one state among the program states.
 17. The storage device of claim16, wherein the controller determines the read failure through an errorcorrection operation.
 18. The storage device of claim 16, wherein eachof the non-volatile memory devices performs the on-chip valley searchread operation in response to the command.
 19. The storage device ofclaim 18, wherein the on-chip valley search read operation includes cellcounting operations corresponding to the at two sensing operations and aselection operation among the sensing operations according to a resultof the cell counting operations.
 20. The storage device of claim 16,wherein the each of the non-volatile memory devices checks a set valueby selecting a page data to be read is a least significant bit (LSB)page data, a center significant bit (CSB) page data, or a mostsignificant bit (MSB) page data and checks an order of applying readsignals to read the selected page data.